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A review on hemeoxygenase-2: focus on cellular protection and oxygen response.

Muñoz-Sánchez J, Chánez-Cárdenas ME - Oxid Med Cell Longev (2014)

Bottom Line: Nevertheless, its abundance in tissues such as testis, endothelial cells, and particularly in brain, has pointed the relevance of HO-2 function.HO-2 presents particular characteristics that made it a unique protein in the HO system.Since attractive results on HO-2 have been arisen in later years, we focused this review in the second isoform.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Patología Vascular Cerebral, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, 14269 Delegación Tlalpan, DF, Mexico.

ABSTRACT
Hemeoxygenase (HO) system is responsible for cellular heme degradation to biliverdin, iron, and carbon monoxide. Two isoforms have been reported to date. Homologous HO-1 and HO-2 are microsomal proteins with more than 45% residue identity, share a similar fold and catalyze the same reaction. However, important differences between isoforms also exist. HO-1 isoform has been extensively studied mainly by its ability to respond to cellular stresses such as hemin, nitric oxide donors, oxidative damage, hypoxia, hyperthermia, and heavy metals, between others. On the contrary, due to its apparently constitutive nature, HO-2 has been less studied. Nevertheless, its abundance in tissues such as testis, endothelial cells, and particularly in brain, has pointed the relevance of HO-2 function. HO-2 presents particular characteristics that made it a unique protein in the HO system. Since attractive results on HO-2 have been arisen in later years, we focused this review in the second isoform. We summarize information on gene description, protein structure, and catalytic activity of HO-2 and particular facts such as its cellular impact and activity regulation. Finally, we call attention on the role of HO-2 in oxygen sensing, discussing proposed hypothesis on heme binding motifs and redox/thiol switches that participate in oxygen sensing as well as evidences of HO-2 response to hypoxia.

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Structure of the Hmox2 and multiple transcripts of rat HO-2. Introns are denoted by thin lines, coding sequences by black boxes. In the promoter sequence, the TATA-like sequence is observed. The upstream regulatory sequence GRE is shown. Nested sequence HMG-17 cDNA is indicated by a green line. Two potential polyadenylation signals are located in the 3′UTR in a purple arrow. The start codon is denoted as +1. Three different transcripts are identified as result of sequence variability in the upstream region from nucleotide −37. Figure based on information reported by [63–65].
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fig3: Structure of the Hmox2 and multiple transcripts of rat HO-2. Introns are denoted by thin lines, coding sequences by black boxes. In the promoter sequence, the TATA-like sequence is observed. The upstream regulatory sequence GRE is shown. Nested sequence HMG-17 cDNA is indicated by a green line. Two potential polyadenylation signals are located in the 3′UTR in a purple arrow. The start codon is denoted as +1. Three different transcripts are identified as result of sequence variability in the upstream region from nucleotide −37. Figure based on information reported by [63–65].

Mentions: Coding sequence of Hmox1 begins in exon 1, while the Hmox2 start codon is found in exon 2. Hmox2 exon 1 is composed entirely of the noncoding sequence 5′UTR [63] (Figure 3).


A review on hemeoxygenase-2: focus on cellular protection and oxygen response.

Muñoz-Sánchez J, Chánez-Cárdenas ME - Oxid Med Cell Longev (2014)

Structure of the Hmox2 and multiple transcripts of rat HO-2. Introns are denoted by thin lines, coding sequences by black boxes. In the promoter sequence, the TATA-like sequence is observed. The upstream regulatory sequence GRE is shown. Nested sequence HMG-17 cDNA is indicated by a green line. Two potential polyadenylation signals are located in the 3′UTR in a purple arrow. The start codon is denoted as +1. Three different transcripts are identified as result of sequence variability in the upstream region from nucleotide −37. Figure based on information reported by [63–65].
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4127239&req=5

fig3: Structure of the Hmox2 and multiple transcripts of rat HO-2. Introns are denoted by thin lines, coding sequences by black boxes. In the promoter sequence, the TATA-like sequence is observed. The upstream regulatory sequence GRE is shown. Nested sequence HMG-17 cDNA is indicated by a green line. Two potential polyadenylation signals are located in the 3′UTR in a purple arrow. The start codon is denoted as +1. Three different transcripts are identified as result of sequence variability in the upstream region from nucleotide −37. Figure based on information reported by [63–65].
Mentions: Coding sequence of Hmox1 begins in exon 1, while the Hmox2 start codon is found in exon 2. Hmox2 exon 1 is composed entirely of the noncoding sequence 5′UTR [63] (Figure 3).

Bottom Line: Nevertheless, its abundance in tissues such as testis, endothelial cells, and particularly in brain, has pointed the relevance of HO-2 function.HO-2 presents particular characteristics that made it a unique protein in the HO system.Since attractive results on HO-2 have been arisen in later years, we focused this review in the second isoform.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Patología Vascular Cerebral, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, 14269 Delegación Tlalpan, DF, Mexico.

ABSTRACT
Hemeoxygenase (HO) system is responsible for cellular heme degradation to biliverdin, iron, and carbon monoxide. Two isoforms have been reported to date. Homologous HO-1 and HO-2 are microsomal proteins with more than 45% residue identity, share a similar fold and catalyze the same reaction. However, important differences between isoforms also exist. HO-1 isoform has been extensively studied mainly by its ability to respond to cellular stresses such as hemin, nitric oxide donors, oxidative damage, hypoxia, hyperthermia, and heavy metals, between others. On the contrary, due to its apparently constitutive nature, HO-2 has been less studied. Nevertheless, its abundance in tissues such as testis, endothelial cells, and particularly in brain, has pointed the relevance of HO-2 function. HO-2 presents particular characteristics that made it a unique protein in the HO system. Since attractive results on HO-2 have been arisen in later years, we focused this review in the second isoform. We summarize information on gene description, protein structure, and catalytic activity of HO-2 and particular facts such as its cellular impact and activity regulation. Finally, we call attention on the role of HO-2 in oxygen sensing, discussing proposed hypothesis on heme binding motifs and redox/thiol switches that participate in oxygen sensing as well as evidences of HO-2 response to hypoxia.

Show MeSH
Related in: MedlinePlus